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Path: utzoo!mnetor!seismo!rutgers!mit-eddie!genrad!decvax!eagle_snax!geoff
From: geoff@eagle_snax.UUCP ( R.H. coast near the top)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Automatic IP address assignment
Message-ID: <127@eagle_snax.UUCP>
Date: Mon, 22-Jun-87 07:52:37 EDT
Article-I.D.: eagle_sn.127
Posted: Mon Jun 22 07:52:37 1987
Date-Received: Tue, 23-Jun-87 04:22:52 EDT
References: <8706121831.AA05760@saturn.mitre.org>
Lines: 34
Summary: PCs have rights too!

In article <8706121831.AA05760@saturn.mitre.org>, lazear@GATEWAY.MITRE.ORG writes:
> Geoff,
> 	I am surprised nobody has mentioned the issue of how does
> someone off-net ever address anything to the PC-host?  There has
> been no notion of updating a name server to be able to tell remote
> systems the PC's address (what if the remote system caches it?).
> I think this impacts the duration of the IP/PC binding, since re-
> using an IP address means former associations are now void implicitly.

Quite apart from the (not unreasonable) idea of off-net nodes
addressing the PC, an off-net server system may well need to map the
client PC's IP address into a hostname or vice versa. For example, the Sun
NFS mount daemon performs a consistency check on the mount request
by taking the hostname passed in the RPC arguments, doing a 'gethostbyname'
on it, and verifying that the RPC did indeed originate from that
address. It can then confidently use the name to check the 'netgroups'
access control list. As you say, a completely dynamic address assignment
scheme would require that the name-address mapping be propagated to all
servers which might have cached a previous mapping.

> ....  Perhaps the mainframe (as
> I characterize non-PC hosts) has no need to contact the PC or try to
> deliver datagrams to it until the PC comes up and announces itself?
> 	Walt Lazear

As I've indicated, I think this is unduly restrictive. But again, it
all depends which problem you're trying to solve: sharing scarce
resources (IP addresses) or making the installation of network
nodes simpler and less error-prone.
-- 
"You want a disclaimer form? Next window, please..."

Geoff Arnold, Sun Microsystems East Coast Division (home of PC-NFS)
UUCP: {ihnp4,decwrl,...}!sun!garnold  ARPA: garnold@sun.com